Augmentation or reconstruction of the breast through the use of implantable medical prostheses is commonly used in reconstructive and plastic surgery.
The prostheses used for these procedures have a basic problem associated with the upper pole, namely, insufficient rigidity to maintain the upper pole when in a vertical position. Undesirable alterations of the breast shape are often observed which are commonly referred to as prosthesis wrinkling, knuckling, or scalloping. Usually, these adverse phenomena are observed at the poles of the prosthesis or along the perimeter of the prosthesis shell.
In order to maintain the shape of the upper pole, attempts have been made to use a gel-type filling with a more rigid consistency which, however, leads to a firmer feeling implant, which often appears unnatural and thus is not desirable. On the other hand, a prosthesis with a soft and thus naturally feeling consistency shows a particular risk of the above-mentioned adverse effects.
European Patent Publication No. 0 804 910 discloses an external breast prosthesis of two shell-shaped bodies made of silicone composition of different thickness and each welded into plastic films, the outer body simulating the breast shape and having a hardness matching the soft resilient composition of the natural breast tissue, and the inner body having a softer gel-like consistency which prosthesis is being provided with a permanently tacky adhesive layer which layer comprises first area arranged on the outer prosthesis body and a second area arranged on the inner body thereof.
The prosthesis in accordance with European Patent Publication No. 0 804 910 is not implanted into the body but is attached to the body of the wearer through the mentioned adhesive layers and thus is not a breast implant.
European Patent Publication No. 2 286 761 discloses a form-stable implant comprising an elastomeric shell having anterior and posterior portions, superior and inferior aspects and a perimeter region where the anterior and posterior portions meet, and a plurality of cohesive gel fillers having at least two different degrees of gel cohesiveness. Preferably the gel cohesiveness is greatest at the inferior portion of the implant. According to FIG. 3 of European Patent Publication No. 2 286 761, the gel cohesiveness may be greatest in the upper aspect of the implant. The more cohesive gel is primarily extending along the posterior portion of the implant.
U.S. Pat. No. 3,671,787 discloses a breast prosthesis suitable for implanting into the human breast comprising a container filled with silicone rubber gels of varying stiffness with the stiffest, most viscous gel filling the outer portion of the container and less viscous gels forming further layers with the center portion being filled with the softest material. The outer layers as well as the further layers extend from the anterior part to the posterior part of the container, i.e., they are positioned horizontally.